Production device for calcium carbonate

Abstract

To provide a new production device for calcium carbonate which can suitably produce calcium carbonate.SOLUTION: A production device for calcium carbonate according to the present invention is a production device E which reacts a raw material containing calcium hydroxide and gas containing carbon dioxide to produce calcium carbonate. The production device includes: stirring means 20 which stirs the raw material; a tightly-closable reaction tank 10 which is provided with the stirring means 20 in the inside thereof; and gas supply means 30 which supplies the gas to the inside of the rection tank 10.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an apparatus for producing calcium carbonate. [Background technology]

[0002] In recent years, efforts have been made to achieve carbon neutrality through "carbon recycling," which involves recovering and effectively utilizing CO2 (carbon dioxide) as a resource to reduce CO2 emissions. The applicant of the present application has proposed a hydraulic composition containing a predetermined amount of calcium carbonate, as disclosed in Patent Document 1. This hydraulic composition not only reduces CO2 emissions by reducing the amount of cement used while maintaining material properties such as strength, but also immobilizes CO2 inside the concrete as calcium carbonate.

[0003] Regarding the method for producing calcium carbonate used in Patent Document 1, various techniques have been proposed up to now. For example, Patent Document 2 proposes a method for producing precipitated calcium carbonate by mixing seed crystals with one or both of an aqueous suspension of calcium hydroxide and an aqueous suspension of partially carbonated calcium hydroxide, and then blowing carbon dioxide or a gas containing carbon dioxide into the resulting aqueous suspension to carbonate it, in which the mixing is carried out by a shear stirring treatment at a stirring peripheral speed of 7 m / s or more. Furthermore, Patent Document 3 proposes a method in which an alkaline agent is added to waste seawater after producing magnesium hydroxide from seawater to adjust the pH to greater than 11 and equal to or less than 13, and a gas containing carbon dioxide is reacted with the calcium component of the waste seawater for a preset time that increases as the pH of the waste seawater to which the alkaline agent has been added increases. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2021 / 256484 [Patent Document 2] Japanese Patent Application Publication No. 11-11941 [Patent Document 3] Patent No. 7138256 Summary of the Invention [Problem to be solved by the invention]

[0005] The calcium carbonate production methods of Patent Documents 2 and 3 are both methods in which a gas containing carbon dioxide is blown into a solution containing calcium ions (so-called liquid phase method). Therefore, the methods for producing calcium carbonate in Patent Documents 2 and 3 require a large amount of water to disperse the raw materials, and may also require a prior treatment of the raw materials (shear stirring treatment in Patent Document 2) or pH control in the liquid phase (adjustment treatment in Patent Document 3). Therefore, the present inventors have wanted to produce calcium carbonate by a method that is completely different from the liquid phase methods of Patent Documents 2 and 3. Specifically, this is a production method in which calcium carbonate is produced by reacting a raw material containing calcium hydroxide with a gas containing carbon dioxide (solid phase reaction: strictly speaking, a reaction between a solid and a gas). In order to put this manufacturing method into practical use, the present inventors wanted to create a manufacturing apparatus suitable for this manufacturing method.

[0006] From this viewpoint, an object of the present invention is to provide a new calcium carbonate production apparatus capable of appropriately producing calcium carbonate. [Means for solving the problem]

[0007] The above problems can be solved by the following means. The calcium carbonate production apparatus according to the present invention is a production apparatus for producing calcium carbonate by reacting a raw material containing calcium hydroxide with a gas containing carbon dioxide, and includes: a stirring means for stirring the raw material; a sealable reaction vessel having the stirring means installed therein; and a gas supply means for supplying the gas into the reaction vessel. According to the present invention, by supplying gas by the gas supply means while stirring the raw materials by the stirring means, it is possible to disintegrate powders with large particle diameters contained in the raw materials and to appropriately mix the raw materials with the gas. As a result, the reaction "Ca(OH)2 + CO2 → CaCO3 + H2O" occurs in the reaction tank, and calcium carbonate can be appropriately produced. The gas supply means of the calcium carbonate production apparatus according to the present invention supplies the gas from the lower side of the reaction tank. According to the present invention, the entire interior of the reaction vessel can be filled with gas, so that the above reaction occurs more appropriately. The calcium carbonate production apparatus according to the present invention includes a temperature control means for controlling the temperature inside the reaction tank. The temperature control means controls the temperature inside the reaction tank by circulating a liquid around the reaction tank or by supplying high-temperature steam. According to the present invention, the raw material can be dried by the temperature control means to keep the moisture content of the raw material within a predetermined range (specifically, below a predetermined value), thereby increasing the amount of calcium carbonate produced. The calcium carbonate production apparatus according to the present invention includes a water supply means for supplying water into the reaction tank. According to the present invention, water can be added to the raw material by the water supply means to adjust the moisture content of the raw material to within a predetermined range (specifically, a predetermined value or more), thereby increasing the amount of calcium carbonate produced. The calcium carbonate production apparatus according to the present invention includes a measuring means for measuring the carbon dioxide concentration of the gas discharged from the reaction tank. According to the present invention, the increase in carbon dioxide concentration in the discharged gas can be confirmed by the measuring means, so that the appropriate timing for stopping work can be determined. The calcium carbonate production apparatus according to the present invention includes a recovery means for recovering the gas discharged from the reaction tank, and a circulation means for supplying the gas recovered by the recovery means to the reaction tank. According to the present invention, the gas recovered by the recovery means can be supplied to the reaction vessel by the circulation means, so that the amount of gas used can be reduced, leading to reduced production costs and improved efficiency. [Effects of the Invention]

[0008] According to the calcium carbonate manufacturing apparatus of the present invention, calcium carbonate can be manufactured appropriately. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram of an entire calcium carbonate manufacturing apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a side view of the inside of a reaction tank of the calcium carbonate production apparatus according to the present embodiment, as seen from the side. [Figure 3] FIG. 2 is a top view of the inside of a reaction tank of the calcium carbonate production apparatus according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the calcium carbonate manufacturing apparatus according to the present invention will be described with reference to the drawings. [Calcium carbonate manufacturing equipment] Fig. 1 is a schematic diagram of the entire apparatus for producing calcium carbonate according to this embodiment. Fig. 2 is a side view of the inside of a reaction tank. Fig. 3 is a top view of the inside of a reaction tank. As shown in Fig. 1, the calcium carbonate production apparatus E according to this embodiment includes a reaction tank 10, a gas supply means 30, a temperature control means 40, a water supply means 50, a measurement means 60, a recovery means 70, and a circulation means 80. As shown in Figs. 2 and 3, a stirring means 20 is provided inside the reaction tank 10. Hereinafter, each component of the calcium carbonate production apparatus E according to this embodiment will be described in detail.

[0011] (Reaction tank) The reaction vessel 10 is a vessel where the raw material and gas are reacted with each other. The reaction vessel 10 includes a vessel body 11 having a substantially rectangular parallelepiped interior and an open top, and a lid 12 that closes the upper opening of the vessel body 11. The lid 12 can seal the interior of the reaction vessel 10. Note that the seal can be formed to a level that can prevent gas leakage that would interfere with the reaction. The bottom surface of the tank body 11 is curved so as to follow the rotational path of blades 22 of the stirring means 20, which will be described later. In addition, a gas flow path 13 is provided on the bottom surface of the tank body 11. A water supply port (not shown) and a gas recovery port (not shown) are provided on the lid 12. The downstream end of a pipe t4 of the water supply means 50 (described later) is connected to the water supply port. The upstream end of a pipe t6 of the recovery means 70 (described later) is connected to the gas supply port. The size and shape of the inside of the reaction vessel 10 are not particularly limited, and may be set appropriately depending on the shape of the stirring means 20 provided inside and the amount of raw materials to be introduced.

[0012] (stirring means) The stirring means 20 is a means for stirring the raw material and gas inside the reaction vessel 10. The stirring means 20 includes two cylindrical rotating shafts 21 and a plurality of blades 22 fixed to each rotating shaft 21. The rotating shafts 21 extend inward from holes 14 in the side surface of the tank body 11. Six blades 22 are fixed to each rotating shaft 21 by fasteners 23 (nuts). To achieve proper stirring, the blades 22 are fixed so that the surfaces of the blades 22 are inclined at a predetermined angle θ (for example, 20 to 40°, 25 to 35°) with respect to a plane perpendicular to the axial direction of the rotating shafts 21. The blades 22 are coated with fluororesin (fluorinated ethylene propylene resin: FEP resin), which prevents poor mixing caused by the raw materials adhering to the blades 22. Furthermore, by setting the distance W between the tip of the blades 22 and the inner surface (bottom or side) of the tank body 11 to 7 mm or less, poor mixing caused by the raw materials adhering to the tank body 11 can be prevented. The blades 22 are wedge-shaped with a thin base and a large tip, and since the tip is arc-shaped, they can also be said to be fan-shaped. In addition, in order to prevent the raw material from leaking (backflowing) in the gap between the rotating shaft 21 of the stirring means 20 and the hole 14 on the side of the tank body 11, a backflow prevention mechanism (not shown) is provided to send air from the outside to the inside of the gap. The number of rotating shafts 21, the number of blades 22, the shape of the blades 22, etc. are not particularly limited and may be set appropriately depending on the internal size of the reaction vessel 10 and the amount of raw material introduced.

[0013] (Gas supply means) The gas supply means 30 is a means for supplying gas into the reaction vessel 10 . The gas supply means 30 includes a gas storage section 31 for storing gas, and a pipe t1 for supplying the gas stored in the gas storage section 31 to the reaction vessel 10. The gas storage section 31 is not particularly limited as long as it is a mechanism capable of storing gases such as exhaust gas, which will be described later. The upstream end of the pipe t1 is connected to the gas storage section 31, and the downstream end is connected to the lower side of the reaction tank 10 (more specifically, to the gas flow path 13 provided on the bottom surface of the tank body 11). Gas is supplied from a slit-shaped gas supply port P provided in the gas flow path 13 so as to be distributed throughout the entire interior of the reaction tank 10. The gas supply means 30 is only required to be able to supply gas into the interior of the reaction tank 10 from the "below side," and this "below side" is not particularly limited as long as it is a location below the center of the reaction tank 10 in the vertical direction, and may be the side of the reaction tank 10 or the boundary between the bottom and side (the curved portion in Figure 2).

[0014] (Temperature control means) The temperature control means 40 is a means for controlling the temperature inside the reaction vessel 10 . The temperature control means 40 comprises a hot water unit 41 that produces liquid at a predetermined temperature, a liquid circulation jacket 42 that circulates the liquid around the reaction tank 10, a pipe t2 that supplies liquid from the hot water unit 41 to the liquid circulation jacket 42, and a pipe t3 that returns the liquid from the liquid circulation jacket 42 to the hot water unit 41. The temperature control means 40 further includes a heat insulating material (not shown) that is located inside the liquid circulation jacket 42 and covers the outside of the reaction vessel 10. Known devices may be used for the hot water unit 41 and the liquid circulation jacket 42, and known materials may be used for the heat insulating material. Also, instead of circulating a liquid, high-temperature steam (the temperature of the steam is not particularly limited as long as it is equal to or higher than the temperature inside the reaction tank 10) may be supplied.

[0015] (Water supply means) The water supply means 50 is a means for supplying water to the inside of the reaction vessel 10 . The water supply means 50 includes a water storage section 51 for storing water, and a pipe t4 for supplying the water stored in the water storage section 51 to the reaction tank 10. There are no particular limitations on the water storage unit 51 as long as it is a mechanism that can store water. The upstream end of the pipe t4 is connected to the water storage unit 51, and the downstream end is connected to the upper side of the reaction tank 10 (more specifically, to the water supply port provided in the lid 12).

[0016] (Measuring means) The measuring means 60 is a means for measuring the carbon dioxide concentration of the gas discharged from the reaction vessel 10. The measuring means 60 includes a measuring instrument 61 for measuring the carbon dioxide concentration, and a pipe t5 for supplying the gas discharged from the reaction vessel 10 to the measuring instrument 61. The measuring instrument 61 may be a known instrument.

[0017] (Means of collection) The recovery means 70 is a means for recovering the gas discharged from the reaction vessel 10 . The recovery means 70 includes a gas recovery section 71 that stores the gas discharged from the reaction vessel 10, and a pipe t6 that supplies the gas discharged from the reaction vessel 10 to the gas recovery section 71. The gas recovery unit 71 is not particularly limited as long as it is a mechanism that can store gas. The upstream end of the pipe t6 is connected to the upper side of the reaction vessel 10 (more specifically, to the gas recovery port provided in the lid 12), and the downstream end is connected to the gas recovery unit 71.

[0018] (circulation means) The circulation means 80 is a means for supplying the gas recovered by the recovery means 70 to the reaction vessel 10 . The circulation means 80 is equipped with a pipe t7, the upstream end of which is connected to the gas recovery section 71 and the downstream end of which is connected to the lower side of the reaction tank 10 (more specifically, to the gas flow path 13 provided on the bottom surface of the tank body 11).

[0019] (Control means) The control means (not shown) is a means for controlling the amount of gas supplied from the gas supply means 30, the amount of water supplied from the water supply means 50, the temperature inside the reaction vessel 10, the suspension of work, and the like. The control means is realized by a program execution process by a CPU (Central Processing Unit), a dedicated circuit, etc. The storage unit provided in the control means can be configured with a general storage device such as a RAM (Random Access Memory), a ROM (Read Only Memory), an HDD (Hard Disk Drive), or a flash memory. The control method by the control means will be described in detail later.

[0020] (Other configurations) Each of the pipes t1 to t7 may be appropriately provided with a pump or valve capable of adjusting the flow rate of a fluid (liquid or gas), a flow meter capable of measuring the flow rate of a fluid, and the like. A thermometer capable of measuring the temperature inside the reaction vessel 10 may also be installed.

[0021] [Raw materials] The raw material contains calcium hydroxide. The content of calcium hydroxide in the solid content of the raw material is preferably 30% (specifically w / w%) or more, more preferably 50% or more, 70% or more, 80% or more, or 90% or more. By ensuring that the calcium hydroxide content is a predetermined value or more, it is possible to increase the amount of calcium carbonate produced by reaction with a gas, which will be described later. Furthermore, the raw materials preferably have a moisture content of 40% (w / w) or less during the reaction process (from the start to the end of the reaction), more preferably 0.3 to 40%, 1 to 40%, 5 to 30%, or 10 to 25%. The present inventors have found that by keeping the moisture content of the raw materials within a predetermined range, the carbonation reaction of calcium hydroxide proceeds appropriately, and a large amount of calcium carbonate is produced. The raw material is not particularly limited as long as it satisfies the above two requirements, but examples include sludge (carbide slag) produced as a by-product in the process of producing acetylene gas from calcium carbide, waste concrete, sludge from ready-mixed concrete, cement, etc., and one or more of these can be suitably crushed and used. Among these, it is particularly preferable to use carbide slag, which is a by-product (residue) and has a high calcium hydroxide content. Since the raw material has the above-mentioned moisture content, it is not in the state of a solution as in Patent Documents 1 and 2, but in the state of a slurry or powder.

[0022] [gas] The gas contains carbon dioxide. Examples of gas that can be used include exhaust gas from a boiler (with a carbon dioxide concentration of about 10%) and carbon dioxide gas that has been highly concentrated using a concentrator. From the viewpoint of the rate of calcium carbonate production, the carbon dioxide content in the gas should be 5% (specifically, v / v%) or more. When the carbon dioxide content in the gas is 5% or more, the carbonation reaction can be rapidly advanced, and calcium carbonate can be produced in a short time. On the other hand, from the viewpoint of the final amount of calcium carbonate produced, it is better for the gas to have a higher carbon dioxide content, but even if the carbon dioxide content is too high, the amount of calcium carbonate produced does not change much. Therefore, from the viewpoint of economy (the exhaust gas can be used as it is, or can be used after a slight concentration treatment), the carbon dioxide content in the gas is preferably 80% or less, more preferably 60% or less, and more preferably 50% or less.

[0023] [How calcium carbonate manufacturing equipment is used] A mode of use of the calcium carbonate manufacturing device according to this embodiment will be described. (Reaction step) First, raw materials (raw materials containing calcium hydroxide) are placed inside the tank body 11 of the reaction tank 10. Then, the lid 12 is closed to seal the inside. Thereafter, while the raw materials are stirred by the stirring means 20, gas (the gas containing carbon dioxide described above) is supplied from the gas supply means 30, causing the reaction "Ca(OH)2 + CO2 → CaCO3 + H2O". The rotation speed of the blades 22 of the stirring means 20 is not particularly limited, but may be, for example, 10 to 40 rpm. By supplying gas while stirring the raw material with the blades 22 of the stirring means 20, powders with large particle diameters contained in the raw material can be disintegrated, even if they are present, and the reaction can be promoted by appropriately mixing the raw material and the gas. Furthermore, the gas supplied from the gas supply means 30 has a higher specific gravity than air and is supplied from the lower side of the reaction tank 10 through the gas supply port P of the gas flow path 13, so that the entire interior of the reaction tank 10 is appropriately filled with the gas.

[0024] (Reaction process: Control of gas supply amount) The amount of gas supplied from the gas supply means 30 to the reaction vessel 10 may be set appropriately depending on the amount of raw material, the carbon dioxide content of the gas, etc. For example, when the amount of raw material is approximately 6 kg, it is 20 to 100 L / min (preferably 50 to 75 L / min). Therefore, when Z kg of raw material is used, the gas supply amount is controlled to be [3.33×Z] to [16.6×Z] L / min (preferably [8.33×Z] to [12.5×Z] L / min).

[0025] (Reaction process: Control of water supply amount) As the reaction "Ca(OH)2 + CO2 → CaCO3 + H2O" occurs in the reaction tank 10, heat of reaction is generated, causing the temperature of the raw materials to rise. As a result, water evaporates from the raw materials, gradually reducing the moisture content of the raw materials. The inventors have confirmed that, in the above reaction, when the moisture content of the raw materials falls below a predetermined value, the amount of calcium carbonate produced decreases. Therefore, water is controlled to be supplied from the water supply means 50 to the raw materials inside the reaction tank 10 so that the moisture content of the raw materials does not fall below the predetermined value. The amount of water supplied may be controlled based on the measured moisture content of the raw material inside the reaction tank 10 at predetermined time intervals (for example, every 5 to 15 minutes), or the amount of water supplied may be specified (for example, 5% of solids / min) through a preliminary test.

[0026] (Reaction process: temperature control) The inventors have confirmed that the amount of calcium carbonate produced in the reaction described above decreases when the moisture content of the raw materials exceeds a predetermined value. Therefore, in order to properly dry the raw materials, the temperature inside the reaction tank 10 is controlled by the temperature control means 40. Regarding temperature control, the temperature may be measured at predetermined time intervals (e.g., every 5 to 15 minutes) using a thermometer (not shown) inside the reaction tank 10 and controlled based on the measured value, or the control content by the temperature control means 40 may be specified (e.g., 20 to 95°C) through preliminary testing. Furthermore, by providing insulation to cover the outside of the reaction tank 10, the reaction heat associated with the above reaction can be confined inside the reaction tank 10, thereby reducing the energy required for temperature control by the temperature control means 40 (liquid circulation jacket 42).

[0027] (Reaction process: Work stoppage control) As the reaction in the reaction vessel 10 progresses, the amount of carbon dioxide reacted (consumption amount) decreases, and the carbon dioxide concentration in the gas discharged from the reaction vessel 10 increases. Therefore, the carbon dioxide concentration may be measured by the measuring means 60 at predetermined time intervals (for example, every 5 to 15 minutes), and the operation may be stopped (controlling each means such as the stirring means 20 and the gas supply means 30 to stop) when the measured value reaches a predetermined value or more. Alternatively, the time at which the reaction is completed (for example, 10 to 130 minutes, 60 to 120 minutes) may be determined in advance by a preliminary test, and the operation may be stopped when that time has elapsed.

[0028] (Reaction process: circulation control) In the above reaction in the reaction tank 10, unreacted carbon dioxide is present in the gas discharged from the reaction tank 10. Therefore, the gas discharged from the reaction tank 10 is recovered by a recovery means 70, and the recovered gas is circulated to the reaction tank 10 by a circulation means 80 under control. In addition, the gas may be controlled to be circulated when the carbon dioxide concentration measured by the measuring means 60 is equal to or greater than a predetermined value (for example, 5% or greater), or the time at which the carbon dioxide concentration in the discharged gas will reach a predetermined value or greater may be determined through a preliminary test, and the gas may be controlled to be circulated after that time has elapsed.

[0029] (After the reaction step) After the reaction step is completed, the product (containing calcium carbonate) produced inside the reaction vessel 10 is removed from the reaction vessel 10. An outlet (not shown) is provided on the side surface of the tank body 11 in the direction of the tip of the rotary shaft 21 in FIG. 3, and the product can be taken out from this outlet.

[0030] (Other processes) Before operating the calcium carbonate production apparatus E according to this embodiment, a preparation step of adjusting the moisture content of the raw materials to be used may be carried out. In the preparation process, if the raw material has a high moisture content, the raw material may be subjected to dehydration treatment such as thickener, filter press, centrifugation, gravity settling, heat drying, natural drying, etc. On the other hand, if the raw material has a low moisture content, the raw material may be subjected to hydration treatment by adding tap water, distilled water, ion-exchanged water, RO water, or a solution separated by the above-mentioned dehydration treatment. In addition, a drying step may be carried out to adjust the moisture content of the product (calcium carbonate-containing product) produced by the calcium carbonate production apparatus E according to this embodiment. In the drying process, as specified in JIS A6201 "Fly ash for concrete" and JIS A5041 "Crushed stone powder for concrete", the product may be dried so that the moisture content (called "moisture" in JIS) is 1.0% or less.

[0031] [Variations] The calcium carbonate production apparatus E may be provided with a dust collecting means such as a bag filter in the pipe t6 or the gas recovery section 71 in order to remove raw materials from the discharged gas. The product outlet of the calcium carbonate production apparatus E may be provided on the bottom surface of the tank body 11 instead of on the side surface of the tank body 11 in the direction of the tip of the rotation shaft 21 in FIG.

[0032] When the moisture content of the raw materials used is relatively high (when the moisture content of the raw materials does not become less than a predetermined value before the reaction is completed), the calcium carbonate production apparatus E may not be provided with the water supply means 50. When the moisture content of the raw materials used is relatively low (when the moisture content of the raw materials does not exceed a predetermined value until the reaction is completed), the calcium carbonate production apparatus E may not be provided with the temperature control means 40. Furthermore, the calcium carbonate production apparatus E may be configured without the measuring means 60, the recovery means 70, and the circulation means 80, as appropriate. [Explanation of symbols]

[0033] 10 Reaction vessel 20 Stirring means 30 Gas supply means 40 Temperature control means 50 Water supply means 60 Measurement methods 70 Recovery Methods 80 Circulation means E. Calcium carbonate manufacturing equipment t1~t7 piping

Claims

1. A manufacturing apparatus for producing calcium carbonate by reacting a raw material containing calcium hydroxide with a gas containing carbon dioxide, comprising: a stirring means for stirring the raw material; a sealable reaction vessel provided with the stirring means therein; and a gas supply means for supplying the gas into the reaction tank.

2. 2. The calcium carbonate manufacturing apparatus according to claim 1, wherein the gas supply means supplies the gas from a lower side of the reaction tank.

3. 3. The calcium carbonate manufacturing apparatus according to claim 1, further comprising a temperature control means for controlling the temperature inside the reaction tank.

4. 4. The calcium carbonate production apparatus according to claim 3, wherein the temperature control means controls the temperature inside the reaction tank by circulating a liquid around the reaction tank or by supplying high-temperature steam.

5. 3. The calcium carbonate production apparatus according to claim 1, further comprising a water supply means for supplying water into the reaction tank.

6. 3. The calcium carbonate manufacturing apparatus according to claim 1, further comprising a measuring means for measuring a carbon dioxide concentration of the gas discharged from the reaction tank.

7. 3. The calcium carbonate production apparatus according to claim 1, further comprising a recovery means for recovering gas discharged from the reaction tank.

8. 8. The calcium carbonate production apparatus according to claim 7, further comprising a circulation means for supplying the gas recovered by the recovery means to the reaction tank.

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